This project is designed to prepare a GMP quality investigational HIV vaccine and complete the preclinical and laboratory studies needed for clinical studies of a multicomponent HIV-1 adenoviral vector vaccine. The hypothesis is that the vaccine will be safe for human administration and elicit immune responses to HIV-1. Subjects receive LCMV vectored vaccine either as a single agent or as part of a prime-boost regimen. The Vaccine Research Center (VRC), NIAID is developing a novel prime-boost HIV vaccine strategy directed at the three most globally prevalent HIV subtypes (clades). VRC's HIV prime-boost candidate is designed to elicit immune responses to HIV sequences from clades A, B and C which together cause about 90 percent of incident HIV infections around the world. In November 2004, the VRC Clinical Trials Core launched a Phase I clinical study (VRC 006) of a multiclade, multigene recombinant adenovector 5 vaccine at the NIH Clinical Center (Bethesda, MD) as the first step in developing the prime-boost regimen. The LCMV product is being evaluated as a second generation vectored vaccine as part of a prime-boost regimen in preparation for future clinical trials.